This invention relates to a wastewater treatment tank with influent gates (to create turbulent flow and reduce influent flow velocity) and a pre-react zone director having an outwardly flared lower portion. The pre-react zone director causes laminar flow of influent below a settling blanket of sludge to avoid disturbing the blanket, thus allowing the blanket to function as a filter and resulting in a clearer supernatant than in conventional tanks.
Wastewater treatment facilities play an important role in society. As urban and rural populations continue to grow, however, these facilities become increasingly overtaxed and unable to meet the demands placed upon them. These increased demands cause many current wastewater treatment plants to operate near or at capacity. In addition, many treatment facilities were originally constructed decades ago, and utilize technology that is currently failing. Failing or inadequate treatment facilities pose an environmental concern, especially in light of increasingly stringent municipal, state, and federal environmental standards.
Due to the odious nature of wastewater treatment facilities, these facilities have often been constructed far from the sources of sewage to minimize exposure to populated areas. As a result, long sewage lines are needed to connect treatment plants to sewage sources. However, the acidic, corrosive and septic nature of wastewater, including hydrogen sulfide gas, which naturally occurs during the wastewater treatment process, causes the breakdown and failure of long sewage pipes.
To alleviate these problems, many areas have undertaken to either construct more treatment facilities, or to increase the efficiency of existing facilities. The construction of new facilities, however, may be blocked by those who fear the negative impact of such a facility in close proximity to urban or rural areas, such as the emanation of offensive odors, and the potential risk of untreated wastewater spillage. Increasing the efficiency of existing plants can come at great cost, and also poses the risk of interrupting current service.
In order to increase efficiency, and to lower consumer costs, many areas have privatized wastewater services. However, like any business, these private wastewater plants must be economically viable, and are faced with maintenance, energy, and other costs, which reduce profits and impede business growth.
Rapid development and population growth of third world countries also pose a significant sanitation and health risk, as wastewater needs cannot be met by current services. Therefore, these areas are especially in need of low cost, highly efficient wastewater treatment plants.
U.S. Pat. No. 5,302,289 to McClung, et al., discloses a wastewater treatment facility having an inlet in which there are a plurality of downwardly angled structures in a downcomer.
U.S. Pat. No. 4,230,570 to Irving discloses an aerator having an inlet having a downward and outward direction at the bottom, and adjacent inlet air provided by a manifold.
U.S. Pat. No. 5,051,213 to Weske discloses a method and apparatus for mixing fluids, which includes tines that are adjacent to gas inlets.
U.S. Pat. No. 4,162,971 to Zlokarnik, et al., discloses the use of deflecting elements to mix liquids and gas.
U.S. Pat. No. 4,081,368 to Block, et al., discloses the use of staggered partitions in treating wastewater.
U.S. Pat. No. 4,505,820 to Eertink discloses the use of multiple separate bioreactors in treating wastewater.
U.S. Pat. No. 4,705,634 to Reimann, et al., discloses the mixing of wastewater and activated sludge in the presence of carrier particles for microorganisms.
U.S. Pat. No. 4,136,023 to Kirk, et al., discloses an apparatus for wastewater treatment in which oxygenated wastewater is directed out through an adjustable flap.
U.S. Pat. No. 5,688,400 to Baxter, Sr. discloses a waste liquid treatment plant, which includes aeration for downwardly flowing liquid, air nozzles, and a conical section.
U.S. Pat. No. 3,804,255 to Speece discloses a recycling gas contact apparatus for waste material, which includes a downflow conducting cone member and bubble injector.
U.S. Pat. No. 4,421,648 to Besik discloses a single reaction tank in a single suspended growth sludge system that includes a conical shaped outlet section.
U.S. Pat. No. 4,452,701 to Garrett, et al., discloses an open-bottomed stilling chamber above an open-topped chamber with a conical outlet.
It is therefore an object of this invention to provide methods and apparatus for a wastewater treatment system, having influent gates and pre-react zone with outwardly flared lower portion to achieve tertiary treatment results (at least in certain fields of use) from a secondary treatment facility using a single tank. In this connection, primary treatment is usually understood to include settling and anaerobic processes, secondary treatment is usually understood to include aerobic processes, and tertiary treatment is usually understood to include filtering.
It is a still further object of this invention to provide methods and apparatus for low-cost, high-efficiency wastewater treatment systems.
It is a still further object of this invention to provide a process and apparatus that substantially reduces production of sewage sludge.
It is a still further object of this invention to provide a process and apparatus that reduces energy consumption by reducing the number of pumps and blowers needed for operation.
It is a still further object of this invention to provide an apparatus with minimal moving parts.
It is a still further object of this invention to provide such methods and apparatus that combines processes to eliminate the need for multiple stage components, thereby eliminating the odors, maintenance and land requirements, and other costs associated with multi-stage complex wastewater systems.
It is a still further object of this invention to provide methods and apparatus resulting in more nutrient and chemical removal than previous wastewater systems.
It is a still further object of this invention to provide methods and apparatus which is simple in construction and operation so that malfunctions can be easily and quickly diagnosed to reduce the costs of repair and maintenance.
It is a still further object of this invention to provide methods and apparatus that are scalable so that multiple smaller decentralized plants can be used instead of large centralized plants with long pipelines, which allows geographic dispersal of such plants and reduction of peak flows of effluent in particular areas.
It is a still further object of this invention to provide methods and apparatus that allow plants of particular capacity to be constructed using up to 50% less land.
It is a still further object of this invention to provide methods and apparatus that can be operated with less manpower.
It is a still further object of this invention to provide methods and apparatus that allow multiple modular plants with continuous influent flow and intermittent decanting to allow the environment to recover between decants, and allows multiple staggered decanting so that common effluent facilities need only have the capacity to handle one or two (or more, but less than all) modules at a time.
It is a still further object of this invention to provide methods and apparatus that can be easily retrofittable to existing properly sized basins.
It is a still further object of this invention to provide methods and apparatus that denitrify the system by both aerobic and anaerobic processes to avoid algae blooms.
These and other objects are achieved by a device to treat influent that includes a basin with an influent gate housing in the basin to receive influent. Influent gates are mounted inside the influent gate housing so that influent flows over the influent gates, creating turbulent flow and aeration in the influent, and reducing flow velocity of the influent. An influent gate bottom is mounted in the basin under the influent gate housing so that influent exiting the bottom portion of the influent gate housing is directed laterally. A pre-react zone director having an outwardly flared lower portion is mounted to the basin and at least partially encloses the influent gate housing. The pre-react zone director defines a main react zone inside the basin, but outside the pre-react zone director, and the lower portion of the pre-react zone director is spaced apart from the bottom of the basin and defines a contact zone between the lower portion and the bottom of the basin. The pre-react zone director decreases influent flow velocity and directs flow of said influent in a laminar fashion through the contact zone and into the main react zone, so that the influent avoids disturbing any settled sludge in the main react zone and allows formation of a supernatant. The influent does not disturb the settled sludge and is filtered through the sludge (which acts as a biological filter) before forming the supernatant, so that the supernatant is comparable to filtered supernatant. Thus, settling (the settling sludge blanket), aerobic processing (passing the supernatant over the gates), anaerobic processing (the biological activity in the settling sludge blanket) and filtering (passing the influent through the settling sludge blanket to form the supernatant) are all performed in a single basin.
This invention substantially reduces sewage sludge production and energy consumption by wastewater treatment systems, by utilizing a non-mechanical process that uses fewer pumps and blowers than a conventional wastewater treatment system, and utilizes a minimum of moving parts. It reduces plant size, and therefore reduces land requirements, by up to approximately 50% from that of conventional wastewater treatment facilities, and requires only approximately 6 months to 1 year of design and construction time. This invention also requires less manpower and maintenance due to fewer components.
Furthermore, as the use of septic tanks is being restricted by state and municipal regulations, affecting both residential and commercial properties, this invention allows for a septic tank replacement, without having to expend time and money to connect these properties to a large centralized system, or to construct an entirely new sewage infrastructure. This is particularly advantageous for remote small scale commercial developments.
This invention therefore allows the construction of smaller plants closer to the sources of sewage, resulting in shorter sewage pipes, which allow a shorter resident time of influent within the pipes, and therefore significantly reduces exposure to sewage and the possibility of failure.
This invention allows a continuous sewage influent flow into a single basin wastewater treatment system. The modular nature of the invention allows multiple basins to be used, thus allowing multiple staggered decanting so that effluent facilities can be shared and do not have to be as large as conventional ones. This intermittent decanting allows the environment to recover between decanting.
The influent flow travels over the influent gates, creating turbulence in the flow and reducing downward flow velocity. The resulting turbulent flow allows air, in the form of minute bubbles, to be mixed into the influent stream, which starts aerating the influent flow. These minute bubbles also cause a reversing action of the influent flow upon contact with the surface of the wastewater in the basin. This reversing action reduces downward velocities, and thus works in conjunction with the influent gates. The exit of the influent gate housing is below the level of wastewater in the basin.
There are preferably one or more influent gates located within the influent gate housing. These gates are preferably located above the lowest normal wastewater level within the basin. To utilize their turbulent flow/aeration properties, however, gates may also be placed below the wastewater level if further flow velocity reduction is required. Although utilizing no gates falls within the operable range of the invention, it is preferable to have at least one gate. Optimally, there should be more than one gate installed to achieve the best quality effluent.
The influent gates are strategically spaced with the first gate preferably placed approximately one diameter down the vertical influent riser from the influent intake. The first gate is optimally placed approximately where the influent would first hit the wall of the influent gate housing on the side opposite the incoming influent flow. Subsequent gates would preferably be mounted on alternating sides of the interior of the influent gate housing. The flow will thus have a horizontal backward/forward motion as it travels vertically down the riser portion of the influent gate housing (the influent riser). Although it is within the operable range of this invention to have the gates placed in many other positions within the influent gate housing, the gates should preferably be placed in a zig-zag manner down the vertical influent riser, spaced apart from each other by approximately the diameter (or width) of the riser. Enough gates should be provided so that the lowest gate is above the lowest wastewater level (bottom water level) expected during normal operation.
It falls within the operable range of the invention for each gate to be aligned at a downward angle between 90 and 180 degrees from the plane of the influent gate housing wall. However, the greater the angle, the greater the likelihood of un-screened debris within the influent stream getting caught on the gate. Therefore, preferably, the gates should be at a downward angle greater than 90 degrees from the plane of the influent gate housing wall. Optimally, the gates should be at a downward angle between 120 and 135 degrees from the plane of the influent gate housing wall.
After flow velocities are reduced utilizing the influent gates, the influent stream then flows through the basin in a laminar fashion via an outwardly flared portion of the pre-react zone, as described below. As the stream flows to the bottom of the vertical riser portion of the influent gate housing, the stream encounters the floor, or bottom fitting, which is designed to stop downward flow velocities. This bottom fitting is preferably placed at a level below the lowest normal wastewater level in the basin (brought about by normal hydraulic equalization of the entire basin). When the influent flow reaches the surface of the wastewater, splashing further reduces the influent flow velocity.
The bottom fitting is preferably a standard xe2x80x9cTxe2x80x9d fitting affixed to the base of the vertical riser portion of the influent gate housing. This xe2x80x9cTxe2x80x9d fitting is preferably of a multi-port design, having two openings to direct the influent flow in a lateral direction, however, it is within the operable range of the invention to have more or less openings.
Alternatively, it is within the operable range of the invention if there were no bottom xe2x80x9cTxe2x80x9d fitting affixed to the bottom of the vertical riser portion of the influent gate housing. In order to achieve downward flow velocity reduction, a disc or platform may be supported above the floor of the basin, preferably with a peg or some other support, directly below the bottom opening of the influent gate housing. In this alternative design form, flow behavior would not change significantly. As discussed above, the influent flow would travel through the vertical riser portion of the influent gate housing, encountering the influent gates, which create turbulent flow and reduce downward flow velocity. Upon contact with the surface of the wastewater, which is above the bottom exit of the influent gate housing, both splash energy and the reversing action of the turbulent flow further reduce downward flow velocity. As the flow continues downward after contact with the surface, it encounters the disc or platform, which then omni-directionally directs flow laterally, as opposed to a xe2x80x9cTxe2x80x9d fitting, which directs flow laterally through ports.
If no bottom fitting is utilized, then the base of the vertical riser portion of the influent gate housing would preferably have a 90 degree lip extending 360 degrees around the bottom exit of the influent gate housing. This lip would act as an upward ceiling to assist in directing the flow laterally. It is within the operable range of the invention to have no lip, but such a lip is preferred to enhance lateral flow out of the influent gate housing. If there are multiple influent gate housings within the pre-react zone director, then the surface of the disc or platform preferably extends to cover the entire opening area of the pre-react zone director. It is within the operable range of the invention for the disc or platform to be in any geometric shape, however, if only one influent gate housing is utilized, it is preferable that the disc or platform be the same shape as the base of the influent gate housing. If multiple influent gate housings are utilized within a single pre-react zone director, then the disc or platform should preferably be the same shape as the base of the pre-react zone director.
After the influent flow undergoes turbulent aeration and velocity reduction in the influent gate housing, influent velocity is reduced further and then directed via the pre-react zone director into the main react zone of the basin for treatment. The pre-react zone director is designed such that one or more walls create a chamber that separates initial influent flows from the rest of the influent within the basin.
This prevents the initial influent flow from mixing with and disturbing the main react zone""s settled biomass during the settle and decant phases of operation. This allows optimal operation of the settled sludge blanket (biomass) as a natural biological filter.
The pre-react zone director utilizes a flap at its base to direct the flow in a laminar fashion into the main react zone. As a result, disturbances of the settled sludge blanket are minimized, thus creating a dense natural biological filter (biomass), which absorbs biological nutrients and chemicals from the influent sewage stream during the settle phases of operation, and thus creating a superior supernatant for decant. Furthermore, the downward and outward direction of the influent allows increased contact between the influent and resulting biomass, which in turn results in more nutrient and chemical removal than previous systems.
It is within the operable range of the invention if the pre-react zone director utilizes any geometric shape, however, it should preferably be either rectangular, square, triangular, or circular to facilitate installation of the flap. The pre-react zone director is preferably affixed to the side of the main basin wall opposite the decanter, and situated in the center of the main basin""s width. It is within the operable range of the invention if the pre-react zone director is suspended in the basin via flotation devices and anchored in some manner, however, it is preferable that the pre-react zone director be affixed and mounted to the basin wall for structural support and aesthetics. Optimally, the pre-react zone director should be mounted on posts, affixed to the basin wall opposite the decanter, in the middle of the basin width, with the posts being affixed to either the bottom or top of the basin. Where this optimal configuration is difficult (such as with fiberglass basins, or basins in which the wall opposite the decanter is curved or otherwise irregularly shaped), it is then preferable to have the pre-react zone director affixed to the top of the basin, or mounted on posts, which are affixed to the bottom of the basin.
The pre-react zone director flap is an angled lip that extends around the entire perimeter of the base of the pre-react zone director. It is within the operable range of the invention that the flap be aligned at an outward angle between 0 and 180 degrees from the plane of the pre-react zone director wall. The flap should preferably be aligned at an outward angle of greater than 90 degrees from the plane of the pre-react zone director wall. Optimally, the flap should be aligned at a down and outward angle of 120 to 135 degrees from the plane of the pre-react zone director wall. This optimal angle alignment allows for optimum laminar flow of the influent into the main react zone.
It is within the operable range of the invention if the leading edge of the flap where the flap is connected to the base of the pre-react zone director is jagged or uneven. However, the leading edge should preferably be square. Optimally, the edge should be rounded to allow optimum laminar flow of the influent, and decrease turbulent flow under the flap. In addition to reducing turbulence and creating laminar flows, the flap also adds structural strength to the pre-react zone director. It has been found that other systems utilizing a react zone need eventual replacement of the react zone walls because those walls tend to fail after continuous flexing caused by turbulent flow during the aeration phases of operation. By reducing this turbulence, the flap reduces the stresses on the pre-react zone director walls, and extends the structural longevity of the pre-react zone director.
The pre-react zone director encloses the influent gate housing(s) within the basin. Because it rests above the floor of the basin, there is a submerged gap between the flap and the basin floor. This gap comprises the contact zone, where the initial influent flow exits the pre-react zone director and comes into contact with the settled sludge blanket within the main react zone. It is within the operable range of the invention if the pre-react zone director comprises a single wall stretching the width of the basin, thereby creating a 180 degree enclosure of the influent gate housing. This thereby creates a 180 degree contact zone, which is within the operable range of the invention. The pre-react zone director should preferably surround the influent gate housing with a minimum of 270 degrees of enclosure, creating a preferred 270 degree contact zone. It is optimal for the pre-react zone director to completely surround the influent gate housing with a 360 degree enclosure, which allows for an optimal 360 degree contact zone, and which makes optimum usage of the biological filter in the settled sludge blanket.
This device eliminates the need for a separate clarifier, aeration basin, and settling basin, as this invention combines all these elements within one basin. The simplicity of this invention thus eliminates the odors, maintenance, land requirements, and other costs associated with other multi-basin complex wastewater systems. Furthermore, aeration basins for other technologies typically are larger than the clarifiers associated with them. This invention allows the basin to act as a unified clarifier and aeration basin during the cyclic aeration cycle, thus achieving the clarification in a basin that is the same size as the aeration basin. This eliminates the need for separate basins, and substantially reduces the need for sludge return lines, and their associated costs.